It has long been desired to maximize fuel economy, power and driveability in diesel fuel powered vehicles while enhancing acceleration, reducing emissions, and preventing hesitation. While it is known to enhance gasoline powered engine performance by employing dispersants to keep valves and fuel injectors clean in port fuel injection engines, such gasoline dispersants are not necessarily effective direct fuel injected diesel engines. The reasons for this unpredictability lie in the many differences between the direct and indirect fuel injected diesel engines and the fuels suitable for such engines.
For example, there is a dramatic difference between indirect fuel injected diesel engines, and more modern high pressure common rail (HPCR), direct fuel injected diesel engines. Also, low sulfur diesel fuels and ultra low sulfur diesel fuels are now common in the marketplace for such engines. A “low sulfur” diesel fuel means a fuel having a sulfur content of 50 ppm by weight or less based on a total weight of the fuel. An “ultra low sulfur” diesel fuel (ULSD) means a fuel having a sulfur content of 15 ppm by weight or less based on a total weight of the fuel. Fuel injectors in an HPCR engine perform at much higher pressures and temperatures compared to older style engines and fuel injection systems. The combination of low sulfur or ULSD and HPCR engines have resulted in a change to the type of injector deposits and frequency of formation of injector deposits now being found in the marketplace.
Over the years, dispersant compositions for diesel fuels have been developed. Dispersant compositions known in the art for use in fuels include compositions that may include polyalkylene succinimides, polyamines and polyalkyl substituted Mannich compounds. Dispersants are suitable for keeping soot and sludge suspended in a fluid, however dispersants are not particularly effective for cleaning surfaces once deposits have formed on the surfaces.
Hence, fuel compositions for direct fuel injected diesel engines often produce undesirable deposits in the engines. Accordingly, improved compositions that can prevent deposit build up, maintaining “as new” cleanliness for the vehicle life are desired. Ideally, the same composition that can clean up dirty fuel injectors restoring performance to the previous “as new” condition would be equally desirable and valuable in the attempt to reduce air borne exhaust emissions and to improve the power performance of the engines.
In accordance with the disclosure, exemplary embodiments provide a diesel fuel composition for an internal combustion engine comprising, a method for improving performance of fuel injectors and a method for cleaning fuel injectors for an internal combustion engine. The fuel composition includes a major amount of diesel fuel and a minor, effective amount of a quaternary ammonium salt having a thermogravimetric analysis (TGA) weight loss of greater than 50 wt. % at 350° C. The amount of quaternary ammonium salt present in the fuel is sufficient to improve performance of a direct fuel injected diesel engine having combusted the composition compared to the performance of such engine having combusted a fuel composition that does not contain the quaternary ammonium salt.
Another embodiment of the disclosure provides a method of improving the injector performance of a direct fuel injected diesel engine. The method includes operating the engine on a fuel composition containing a major amount of fuel and from about 5 to about 200 ppm by weight based on a total weight of the fuel of a quaternary ammonium salt having a thermogravimetric analysis (TGA) weight loss of greater than 50 wt. % at 350° C. The quaternary ammonium salt present in the fuel improves the injector performance of the engine by at least about 80% when measured according to protocol CEC F-98-08 for direct injection.
A further embodiment of the disclosure provides a method of operating a direct fuel injected diesel engine. The method includes combusting in the engine a fuel composition comprising a major amount of fuel and from about 5 to about 200 ppm by weight based on a total weight of the fuel of a quaternary ammonium salt having a thermogravimetrc analysis (TGA) weight loss of greater than 50 wt. % at 350° C. In further embodiments, the TGA weight loss is greater than 70 wt. %, such as greater than 80 wt. %, particularly greater than 90 wt. % weight loss.
Another embodiment of the disclosure provides an additive concentrate for a fuel for use in a direct injected diesel fuel engine. The additive concentrate includes a quaternary ammonium salt having a thermogravimetric analysis (TGA) weight loss of greater than 50 wt. % at 350° C. and at least one component selected from the group consisting of diluents, compatibilizers, corrosion inhibitors, cold flow improvers (CFPP additive), pour point depressants, solvents, demulsifiers, lubricity additives, friction modifiers, amine stabilizers, combustion improvers, dispersants, antioxidants, heat stabilizers, conductivity improvers, metal deactivators, marker dyes, organic nitrate ignition accelerators, and cyclomatic manganese tricarbonyl compounds.
An advantage of the fuel additive described herein is that the additive may not only reduce the amount of deposits forming on direct fuel injectors, but the additive may also be effective to clean up dirty fuel injectors sufficient to provide improved power recovery to the engine.
Additional embodiments and advantages of the disclosure will be set forth in part in the detailed description which follows, and/or can be learned by practice of the disclosure. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure, as claimed.